Alloy steel and articles



United States Patent 3,235,378 ALLOY STEEL AND ARTICLES Paul A.Jennings, Baldwin, Md, assignor to Armco Steel Corporation, Middletown,Ohio, a corporation of Ohio No Drawing. Filed Nov. 14, 1963, Ser. No.323,591

13 Claims. (Cl. 75-128) My application for patent is acontinuation-impart of my copending application, Serial No. 68,627,filed November 14, 1960, now abandoned, and entitled, Alloy Steel andArticles. The invention relates to alloy steels suited to lowtemperature, room temperature and elevated temperature applications, andto various particular products and articles of ultimate use fashionedthereof.

One of the objects of my invention is the provision of an alloy steelwhich is readily hot-rolled at the mill into sheet and strip, as well asrods and wire, and which sheet, strip, rods and wire readily lendthemselves to further reduction by cold-rolling for the sheet and stripand colddrawing for the rods and wire, and to pressing, bending,cold-upsetting, cutting, threading and the like, and by welding andbrazing into desired articles of use.

Another object is the provision of an austenitic stainless steel whichis resistant to corrosion by the combustion products of the leadedgasolines, as well as those of the standard gasolines and other fuelsfor internal combus tion engines, all at high temperatures, temperaturesup to 1800 R; which steel is tough and strong both at high temperaturesand at low temperatures; which steel when made into coiled springs iselastic at both high and low temperatures and resists relaxation; whichsteel is resistant to scaling at high temperatures; and which isadaptable to quick heating to very high temperatures, say up to 2000"F., from the sub-zero temperatures of wintertime and then quick coolingto the sub-Zero temperatures, all without cracking or other failure.

A further object is the provision of various articles of ultimate use,more particularly smog burners of the catalytic or after-burner type forburning the uncombusted products of an internal combustion engine;exhaust mutllers with tightly coiled springs for dissipating the exhaustgases between coils, and controlling noise level, and electrodes ofspark plugs for internal combustion engines, in all of which articlesthere are achieved resistance to scaling and corrosion under the manyvarying conditions of actual practical use along with long life andresistance to carbide-precipitation and intergranular attack and greatlyimproved resistance to corrosion and erosion by the wash and scour ofhot gases.

Other objects of my invention in part will be apparent and in part morefully pointed to during the course of the following disclosure.

Accordingly, my invention will be seen to reside in the combination ofelements, in the composition of ingredients, and in the relation betweeningredients making up the novel steel of my invention, and in particulararticles and products fashioned thereof, all as more particularlydescribed herein and set forth in the claims at the end of thisspecification.

In order to gain a better understanding of certain features of myinvention, it may be noted at this point that the corrosion-resistingsteels and the heat-resisting steels are finding great favor in the art.In general, it may be said that the various corrosion-resisting andheat-resisting Patented Feb. 15, 1966 steels essentially containchromium in the amount of some 10% to 30%, with remainder substantiallyall iron. Where desired, as in many of the grades of corrosionresistingand heat-resisting stainless steels, there additionally is includednickel in amounts ranging from incidental percentages on up to about30%. Manganese, while commonly present in incidental amounts, may rangeup to some 15%, this as a partial substitute for nickel. And silicon,which usually is present in incidental amounts, may be employed inamounts up to 3% or 4% for special purposes. Carbon is present inamounts anywhere from 0.02% to 1.5%. And many of the grades of bothcorrosion-resisting stainless and the heat-resisting steels containspecial additions of molybdenum, tungsten, cobalt, copper, titanium,columbium and vanadium in small amounts.

More particularly, a member of the more popular grades ofcorrosion-resisting and heat-resisting chromium-nickel stainless steelsare the Type 304 (18% to 20% chromium, 8% to 12% nickel, remainderiron), the Type 309 (22% to 24% chromium, 12% to 15% nickel, 2%manganese, and remainder iron), the Type 310 (24% to 26% chromium, 19%to 22% nickel, 2% manganese, and remainder iron), the Type 316 (16% to18% chromium, 10% to 14% nickel, 2.3% molybdenum, and remainder iron),the Type 321 (17% to 19% chromium, 8% to 11% nickel, 0.4% titanium, andremainder iron), and the Type 347 (17% to 19% chromium, 9% to 12%nickel, 0.8% columbium, and remainder iron).

While the many steels identified above are found to have excellentresistance to corrosion in various room temperature applications andeven some elevated temperature applications, and, moreover, aregenerally found to work well in the mill both in hot-rolling from bloomor billet into plate, sheet, strip, bars, wire and other convertedforms, and even work well in cold-rolling into sheet and strip andcold-drawing into wire, the high temperature mechanical properties ofthese steels and their resistance to corrosion and to scaling at hightemperatures in the presence of many media leave much to be desired.Actually, it is found that all of these well known chromium-nickelstainless steels are inclined to corrosion and/ or pitting or localattack when subjected to lead compounds at temperatures of 1150 F. andhigher.

Of the various heat-resisting stainless steels-straight chromiumgradesthe Type 430 (14% to 18% chromium, .5 nickel, and remainder iron)and the Type 446 (23% to 27% chromium, .5 nickel, and remainder iron),the Type 430 is generally considered to possess good high temperatureproperties, and the Type 446 excellent high temperature properties,i.e., resistance to scaling at high temperatures and resistance tocorrosive attack by many of the more common corrosive media. Actually,it is found that these two grades ofier only fair resistance to theattack of various lead compounds at high temperatures. Unfortunately,however, these steels have limitations with respect to shaping andforming as by bending, pressing, cold-heading and other particularfabricating operations.

Accordingly, an object of the present invention is the provision of analloy steel in which there is had a combination of good hot-workingproperties such as hot-rolling into sheet and strip or hot-rolling intobars and wire; good cold-working properties as in the production ofcold-rolled sheet and strip and cold-drawn wire; good forming propertiessuch as bending, pressing, cold-upsetting, cutting, threading, and thelike; good welding and brazing characteristics; and good resistance tocorrosive attack of various lead compounds, especially those encounteredin the combustion products of the leaded fuels, that is, both completelycombusted and incompletely combusted, all under the high temperatureconditions obtaining in the engine and in the exhaust of the usualinternal combustion engine, i.e., the engines of the usual automobile,truck, tractor, bus, lawnmower, boats, etc.

Referring now more particularly to the practice of my invention, Iprovide an alloy steel essentially consisting of the four ingredientsmanganese, chromium, nickel, nitrogen, with remainder substantially alliron. The amount of each of these several ingredents is substantial andis critical. Criticality also lies in the amount of carbon and siliconwhich may be tolerated. Each of these must be maintained at extremelylow value, the carbon not exceeding .05% as a maximum and the siliconnot exceeding .25 as a maximum, and preferably not exceeding .15%,although in those applications where corrosive attack by lead compoundsis not involved the silicon content need not be so limited; the siliconcontent then may range up to 4.0% or more.

Each of the four essential ingredients manganese, chromium, nickel and,nitrogen as well as the two ingredients carbon and silicon which must betolerated, is critical, and so too, the relation between the same. For Ifind, as more particularly pointed out hereinafter, where the percentagefigures and the relation between the same are consistently maintained,the desired results are achieved. Where, however, these percentagefigures are substantially departed from, the desired results are nothad.

Conveniently the steel of my invention is melted in an electric arcfurnace in accordance with practices well known in the art. Followingmelting and finishing in the electric arc furnace, the metal is run intoa suitable ladle for teeming. Ingots of desired size are had which, whenstripped from the molds, are reheated and converted into slabs, bloomsand billets for further conversion as by hot-rolling into plate, sheet,strip, bars, wire, and the like. And where desired, further conversioninto coldrolled sheet and strip and cold-drawn wire. The metal workswell in the hot mill and in the cold mill, as well.

Considering now more particularly the composition of the alloy steel ofmy invention, I provide a stainless steel consisting essentially ofabout .05% max. carbon, 8% to 16% manganese, .25% max. silicon, 19.5% to23.0% chromium, 5.5% to 9.5% nickel, .20% to .40% nitrogen, molybdenumup to 4.0%, and remainder substantially all iron. The phosphorus andsulphur contents of my steel are each limited to about 04% max.

In broadest aspect, however, the steel of my invention consistsessentially of about .05% max. carbon, 8% to 16% manganese, phosphorusand sulphur each up to .04% max., 17.0% to 23.0% chromium, 5.5% to 9.5%nickel, .20% to .40% nitrogen, molybdenum up to 4.0%, and remaindersubstantially all iron. Silicon may be present in amounts up to 4.0% ormore.

A preferred steel in accordance with the teachings of my inventionessentially consists of about .05% max. carbon, 8.0% to 10.0% manganese,.25% max. silicon, 19.5% to 21.0% chromium, 6.00% to 7.00% nickel, .22%to 30% nitrogen, and remainder substantially all iron. As a specificpreference, the silicon content is maintained at a value not exceeding.15

A further preferred steel, according to my invention, essentiallyconsists of about .05% max. carbon, 8.0% to 10.0% manganese, .25% max.silicon, 17.0% to 18.5% chromium, 6.00% to 7.00% nickel, 22% to 30%nitrogen, 2.0% to 2.5% molybdenum, and remainder substantially all iron.Here again, the silicon content of the steel is preferably maintained ata value not exceeding .15%.

The steel of my invention is austenitic and substantially free ofdelta-ferrite in the annealed and cold-Worked conditions. Moreover, theaustenite is fully retained throughout cold-working and cold-forming,there is some hardening effect in the usual fabricating operations suchas shaping, bending, stretching, shrinking, upsetting, cutting,trimming, threading or the like, in the fashioning of sheet and stripmaterial. Also, with cold reductions, as in the cold-drawing of wire andtightly coiling, some hardening is had which is further developed byhardening heattreatment, i.e., heating the coiled wire at a temperatureof some 800 to 1000 F.

In the steel of my invention the composition is in every sense critical.A low carbon content, that is, a carbon content not exceeding .05% max.,is necessary because I find that with a significantly higher carboncontent the steel contains too many precipitated carbides and is moredifficult to process, by hot-working. Moreover, with the higher carboncontent the steel suffers in cold-workability as in the production ofcold-rolled sheet and strip and in the production of cold-drawn wire.With the carbon content not exceeding .05 I find there is sufficientductility in the sheet and strip to permit the fashioning of tubing andforming into various other shapes as by pressing, bending,cold-upsetting and the like. Moreover, the very low carbon contentassures effective welding and brazing without the deteriorating effectsof carbide precipitation within the heat affected zones. The very lowcarbon content also contributes to the excellent corrosion-resistance ofmy steel, partially as a result of freedom from carbide precipitation atelevated temperatures wherein the steel would be partially robbed ofchromium, with consequent loss of corrosion-resistance at roomtemperatures and elevated temperatures, as well.

Similarly, the manganese content of my steel is critical. Manganese isnecessary in order to achieve the desired resistance to lead oxide. Alsoit serves as an excellent vehicle for the high nitrogen content of mysteel, the nitrogen being introduced as nit-rided electrolyticmanganese, as noted above. With a manganese content of less than about8%, there is a possibility of developing porosity in the as-castmaterial because of lowered solubility for nitrogen. And there arepractical and economic reasons for not wanting the manganese to exceed16%; manganese in excess of 16% does not result in any gain in usefulproperties and it is expensive to add because of high melting losses.Furthermore, the corrosion resistance of the steel suffers adverselywith an excess of manganese, especially in the presence of strongreducing acids.

A low silicon content is required since I find that silicon adverselyaffects the resistance of the steel to the corrosive attack of thevarious lead compounds found in the combustion products of the leadedgasolines. In general, the silicon content should not exceed .25% as amaximum and preferably should not exceed .15%, as noted above.

Where the corrosive attack of lead compounds such as the combustionproducts of leaded fuels, is not involved, however, there is nonecessity for restricting the silicon content to the critically lowfigure of .25% max. The silicon content then may amount to as much as4.0% or more, as noted above.

The chromium content of the steel is critical; a chromium content lowerthan about 19.5% results in the loss of the ability to withstand scalingat high temperatures. And where the chromium content exceeds about23.0%, increased difficulty arises in maintaining austenite stability,and as a result, hot-working difficulties are encountered.

The nickel content is important and critical. I find that at least 5.5nickel is necessary to achieve the desired fully austenitic structure.And I find that a nickel content in excess of about 9.5 unduly adds tothe cost of the metal. Moreover, it unduly stiffens the matrix of thesteel, restricts its solubility for carbon, increases the possibilityfor objectionable carbide precipitation, and decreases the resistance ofthe steel to attack by lead oxide and other lead compounds.

In my steel best results are had where the sum of the manganese andnickel contents substantially exceeds 14%. With any substantially lesseramount of manganese and nickel, in total, there is an inclination towardthe formation of ferrite with a consequent loss of the fully austcniticstructure of the metal and a loss of hot-workability.

The nitrogen content, too, is critical; it contributes to the austeniticstructure of the metal, increases the yield strength at all temperaturesand assures high temperature strength. With a nitrogen content less thanabout .20% there is a loss of austenite, also a loss of strength andhardness. With a nitrogen content exceeding about .40%, the steelbecomes much too stiff at hot-rolling temperatures and preventselfective and consistent rolling to the desired thin gauges.

Molybdenum, as noted above, is not an essential ingredient of my steel.Certain advantages, however, are gained by way of a molybdenum additionup to 4.0%. It improves the hot-rolling characteristics of the steel.Moreover, it improves the high temperatures strength of the metal.Additionally, it improves the resistance to lead oxybromide. Moreover,it improves the corrosionresistance of the metal to reducing acids bothat room temperatures and at sub-zero temperatures. An excessive amountof molybdenum, however, adversely affects the scaling resistance of thesteel in that it requires a lowering of the chromium content to preservethe austenite balance, and with the lowering of chromium, the scalingresistance at high temperatures definitely suffers.

The steel of my invention in the form of plate, sheet, strip, bars, rodsand wire is supplied various customer fabricators, the steel usuallybeing in the annealed condition, annealed at the mill at a temperatureof some 1700 to 2000 F. and quenched in air, oil or water. Wheredesired, however, it will be understood that the metal may be suppliedin the hot-rolled condition. Customarily, however, the metal is suppliedin the form of cold-rolled sheet and strip and cold-drawn wire. Themetal is soft, ductile and readily lends itself to a host of formingoperations such as pressing, bending, upsetting, cutting, drilling,threading or other machining. And readily may be welded or brazed as inthe production of particular articles of ultimate use.

The marked superiority of the readily formable austenitic stainlesssteel of my invention for high temperature applications in the presenceof the combustion products of the leaded fuels, this as compared withthe known easily formable stainless steels and other alloys of the priorart, is well pointed up by the comparative test data presented in TableI below:

TABLE II.CI-IEMICAL COMPOSITION OF FOUR HIGH TEMPERATURE ALLOY STEELSGrade Heat No. 0 Mn Si Cr N1 N M0 Invention. R2658 049 8. 64 23 20. 766. 19 32 Invention.-- R2659 038 8. 39 17 17. 66 6. 29 2. 24 Prior Art-R2802 061 8. 75 14 17.87 5.18 Prior Art- 83-105 092 1. 12 26 24. 46 .92

The mechanical properties of the two steels of my invention in the formof strip of about .018 thickness and in the annealed condition are givenin Table III below:

TABLE III.MECHANICAL PROPERTIES OF THE TWO STEELS OF THE PRESENTINVENTION GIVEN IN TABLE II, THESE IN THE ANNEALED CONDITION Tensile0.2%Y.S., Percent E1. Hardness Heat No. Str. p.s.i. p.s.i. in 2" Rb Acomparison of the corrosion-resisting characteristics of my steel andtwo of the best steels of the prior art at several high temperatures,namely 1550 F., l 800 F. and 2000 F., is given below in Table IV and acomparison of the resistance to corrosion by lead oxybromide is given inTable V.

TABLE IV.RESULTS OF LEAD CORROSION TESTS ON THE FOUR STEELS OF TABLE II*Material Thickness, Test Temp., Loss per Sq. inches F. In. in Grams 0451, 550 0. 070 014 1, 550 0. 079 .051 1, 550 0. 054 069 1, 550 0. 074 0451, 800 0. 087 r 014 9, 800 O. 154 40 .051 1, 800 0. 261 068 1, 800 0.173 045 2, 000 0. 307 014 2, 000 0.365 051 2, 000 0. 577 Type 446 068 2,000 0.367

*Corrosion tests in 5 parts oxide by weight, 5 parts lead sulphate, 3parts lead chloride, 2 parts lead bromide, 1 part sulphur.

The comparative weight loss of the four sample steels TABLE I.-RESULTSOF HI G11 TEMPERATURE CORROSION TESTS ON VARIOUS ALLOYS* Percent PercentWt. Loss Alloy Cr Ni Other per sq. in. Remarks in grams 16 720 Verysevere corrosion. 21 228 Severe Fitting. 21 287 Do. 21 275 D o. 18-20.717 Very severe corrosion. 18-20 788 D 0. 18-20 821 D 0. 22-24 907Severe local attack. 24-26 927 Do. 16-18 795 D0. 17-19 216 Moderatecorrosion. 17-19 242 D0. 17-19 367 Do. 17-19 .502 Severe corrosion.14-18 176 Good. 1 1-18 176 D0. Do 14-18 .172 D0. Invention 21 086 Verygood.

*Corrosion tests at 1,800 F. in a composite corrosive mixture consistingof 5 parts lead oxide by weight, 5 parts lead sulphate, 3 parts leadchloride, 2 parts lead bromide, and 1 part sulphur.

in lead oxybromide with exposure for 1 hour at 1550 F. is given in TableV:

The resistance of my steel to scaling at high temperatures, this withintermittent cyclic heating and cooling, as compared to the bestheat-resisting steels of the prior art, is given in the following TableVI:

TABLE VL-RESULTS OF SCALING TESTS OF THE FOUR STEELS OF TABLE II 4Thick- Loss per Sq. Loss Material ness, Temperature and Time In. in IPYInches Grams .045 1,700 F.51 hr. eycles 0. 0232 0. 320 .014 1,700 F.51hr. cycles--- 0. 0446 0.615 051 1,700 F.-51 hr. cycles.-- 0.0217 0.300Type 446- 068 1,700 F.51 hr. cycles-.- 0. 0300 0. 430

The superiority of the steels of my invention in matters of resistanceto corrosion at various high temperatures by a combination of leadcompounds and by lead oxybromide, and in matters of scaling resistanceunder conditions of intermittent and cyclic heating at high temperaturesreadily is apparent from the results presented in Tables IV, V and VIabove. Thus, for example, at a temperature of 2000 F. and in thepresence of a mixture of lead compounds as noted in Table IV, thespecific steels of my invention suffer weight losses of 0.307 and 0.365gram per square inch, while the two best steels of the prior artsufiered losses of 0.577 and 0.367 gram per square inch. With leadoxybromide and at a temperature of 1555" F., as noted in Table V, thecomparison is even more pronounced; the weight losses for the twosepcific steels of my invention amount to only one-half t that sufferedby the two best steels of the prior art. While all four of the steelsshowed reasonably good resistance to scaling with cyclic heating at 1700F., it is noted from Table VI that the specific example of my steel ofthe higher chromium content (and tree of molybdenum) revealed aresistance to scaling much superior to the example of the lower chromiumcontent which does contain molybdenum.

tures encountered in actual use. The heat exchanger of the anti-smogdevice in which the essential parts in contact with the exhaust gasesare fashioned of the steel of my invention is intended to last the lifeof passenger vehicle, truck, tractor, bus or other vehicle upon which itis installed. With the after-burner employing the essential elementsfashioned of the steel of the present invention the conventional mufilermay be dispensed with.

My new steel in the form of cold-drawn wire lends itself readily to theproduction of a tightly coiled helical spring of substantial diameterand length employed as the eflective operational part of an exhaustmufiler for an internal combustion engine. Illustratively, the wire,cold-drawn to a reduction in area of about 30%, is suitably fashionedinto a helical spring of desired length and diameter, following which itis age-hardened by heating at a temperature of some 800 to 1300 F. andair cooling. The elastic quality of the steel at high temperatures andin the presence of the combustion products of the leaded gasolines andother fuels assures effective operation of .the helical spring, withpressure of the exhaust gases expanding the spring to permit egress intothe atmosphere, all without sag or relaxation over prolonged periods ofuse. The spring is well calculated to last the life of the vehicle onwhich the muffler is installed.

The relaxation properties Off cold-drawn and agehardened steel wireaccording to my invention (two different cold-reductions and threedifferent hardening temperatures for each) is given below in Table VII,this under a load of about 40,000 p.s.i. and at a temperature of about850 F. for a period of days time.

TABLE VII.RELAXATION PROPERTIES OF STEEL WIRE OF THE PRESENT INVENTION--[R.T. stress 40,000 p.s.i.'temp. 850 F.tin1e 5 dayswire size .125diameter] Condition: 55322 15% CD+1000 F.2 Hrs. A.C. 10 2 CD+1150 F.2Hrs. A.C. 10.0 15% CD+l300 F.2 Hrs. A.C 6.8 30% C-D+l000 Fa-2 Hrs. A.C9.1 30% CD+1150 F.-2 Hrs. A.C 6.0 30% CD+1300 F.2 Hrs. A.C. 7.3

*Heat 50380 analyzing .039% carbon, 9.26% manganese, .12% sil1con,20.14%chromium, 6.27% nickel, 28% nitrogen. and remainder substantially alliron.

The mechanical properties of the cold-drawn wire of my invention(age-hardened at three different temperatures following cold-reduction)are given in Table VIH, this for wire of about 0.125 diameter.

TABL'E VIII.MECHANICAL PROPERTIES OF THE STEEL WIRE* OF THE PRESENTINVENTION Condition U.T.S., 2% Y.S. Percent Percent Rock p.s.i. p.s.i.El. .A. Hard 15% CD+1,000 132-2 Hrs. 128/128, 000 101/103, 000 56/5668/68 021 15% CD+1,15J F.2 Hrs. 123/127, 000 89/ 97, 000 44/46 67/67 C15% CD+1,300 F.2 Hrs. 120/125, 000 93/ 93, 000 60/60 65/65 C20 CD+1,0001 .-2 Hrs. 179, 000 162,000 28 57 C39 30% CD+1,150 F.2 Hrs. 166/166, 000148/150, 000 28/28 52/56 033 30% CD+1,300 F.2 Hrs. 159/159, 000 140/141,000 /40 56/59 C30 Heat 50380 whose chemical analysis is given as afootnote to Table VII.

The steel of my invention in the form of cold-rolled strip, as notedabove, is particularly suited to the production of various parts of ananti-smog device whether combustion chamber, heat chamber, after burneror other components for handling the exhaust gases of various internalcombustion engines, notably passenger vehicles, trucks, tractors, buses,and the like. The cold-rolled sheet or strip elfectively lends itself tofabrication into a liner :for the combustion chamber of theafter-burner. Also it readily may be formed into the required manifoldshell. Applicant finds that the steel well resists the corrosive attackof the various combustion products of the From the data given in TablesVII and VIII it rather clearly appears that the best combination ofmechanical properties and relaxation properties are bad with a coldreduction of about 30% followed by ageing at a temperature of about1150" F. for two hours. Note that with this treatment there is had anultimate tensile strength of 166,000 p.s.i. and a yield strength of148,000 p.s.i. with a relaxation loss in load of only 6.8%. This samelow relaxation loss is had in wire of 15% cold-reduction but theultimate and yield strengths there only come to about 123,000 and 89,000p.s.i., respectively.

In addition to the production of an anti-smog device leaded fuels andother fuels at high operating temperaand the helical spring component ofan internal com- 9 bustion engine mufiier, my steel is well suited tothe production of the electrodes employed in the spark plug for aninternal combustion engine. In this application both the centerelectrode of the plug and the outside electrode are fashioned of thesteel wire of my invention. The metal readily lends itself to welding byconventional methods, permitting a secure weld between the outsideelectrode and the metal shell of the plug. The thermal conductivity ofthe electrodes is adequate and the electrodes resist the Wash, scour andcorrosive attack of the internal combustion engine gases. Moreover, theelectrodes present good resistance to erosion by electric spark.Resistance to oxidation is good at the temperatures encountered inactual use, temperatures ranging up to 1800 F.

In the steel of my invention and in the various articles fabricatedthereof there is achieved excellent resistance to the corrosive attackof various lead compounds at high temperatures, all as encountered inthe exhaust gases of internal combustion engines, particularly thecombustion products of the leaded fuels. The steel is resistant tooxidation and scaling at high temperatures. And Whether in the form ofsheet or strip or in the form of cold-drawn wire it adequately resistscorrosion, scaling under the wash and scour of the hot exhaust gases ofthe internal combustion engine whether completely or incompletelyburned. And in the form of cold.drawn and agehardened wire there isachieved not only good resistance to corrosion by the exhaust gases andresistance to scaling, but excellent mechanical properties, as well,particularly the properties of elasticity and relaxation.

Thus it will be seen that I provide in my invention a ductile andreadily formable manganese-chromium-nickelnitrogen austenitic stainlesssteel of critically low carbon and silicon contents in which the manyobjects hereinbefore set forth together with many practical advantagesare successfully achieved. Moreover, it will be seen that I providestainless steel sheet and strip, possessing a combination ofcorrosion-resisting and scale-resisting properties along with excellentformability and good Welding and brazing characteristics. The brazed orWelded products are free of carbide precipitation difiiculties withinthe heat affected areas. I also provide cold-drawn stainless steel wireof high quality as noted above. The steel of my invention, whether inthe form of plate, sheet, strip, bars, rods, wire, and the like, readilylends itself to fabrication into a host of articles of ultimate use, inwhich articles there are enjoyed the combination of ductility and goodformability, along with strength and toughness at elevated temperaturesand excellent resistance to scaling and corrosion by the combustionproducts of the leaded fuels and other fuels employed in the internalcombustion engine.

While all of the beneficial properties characterizing my steel are hadonly where the silicon content is restricted to the critically lowfigure of .25% max., the beneficial Working, forming, Welding, brazingand agehardening properties, with resultant strength and toughness, infact all benefits excepting resistance to the corrosive attack by leadcompounds, are achieved when the silicon content is not restricted to.25 max.

Since many embodiments may be made of my invention and since manyvariations may be made in the several embodiments hereinbefore setforth, it will be understood that all matter described herein is to beinterpreted as illustrative and not as a limitation.

Having described my invention, I claim:

1. An alloy steel having good hot-rolling, good coldforming, goodWelding and good scaling resistance properties, said steel essentiallyconsisting of about: 8% to 16% manganese, 17.0% to 23.0% chromium, 5.5%to 9.5% nickel, .20% to .40% nitrogen, carbon not exceeding .05%,silicon up to 4.0% or more, and remainder essentially iron.

2. An alloy steel having good hot-rolling, good coldforming, goodWelding and good scaling resistance prop- 10 erties, said steelessentially consisting of about: 8% to 16% manganese, 19.5% to 23.0%chromium, 5.5% to 9.5% nickel, 20% to .40% nitrogen, carbon not exceeding .05 silicon up to 4.0%, and remainder essentially iron.

3. An alloy steel having good hot-rolling, good coldforming and goodwelding properties, said steel essentially consisting of about: 8.0% to10.0% manganese, 19.5% to 21.0% chromium, 6.00% to 7.00% nickel, .22% to30% nitrogen, carbon not exceeding .05 and remainder essentially iron.

4. An alloy steel having good hot-rolling, good cold forming and goodWelding properties, said steel essentially consisting of about: 8.0% to10.0% manganese, 20.0% to 21.0% chromium, 6.25% to 6.75% nickel, .22% to.30% nitrogen, carbon not exceeding .05%, and remainder essentiallyiron.

5. An alloy steel having good hot-rolling, good coldforming and goodwelding properties, and good corrosionresistance and scaling resistance,said steel essentially consisting of about: 8% to 16% manganese, 19.5%to 23.0% chromium, 5.5% to 9.5% nickel, 20% to .40% nitrogen, carbon notexceeding .05%, silicon not exceeding .25%, and the remainderessentially iron.

6. An alloy steel having good hot-rolling, good coldforming and goodWelding properties, and good corrosion-resistance and scalingresistance, said steel essentially consisting of about: 8.0% to 10.0%manganese, 19.5% to 21.0% chromium, 6.0% to 7.00% nickel, .22% to 30%nitrogen, carbon not exceeding 05%, silicon not exceeding .25%, andremainder essentially iron.

7. An alloy steel having good hot-rolling, good coldforming and goodwelding properties, and good corrosion-resistance, said steelessentially consisting of about: 8.0% to 10.0% manganese, 20.0% to 21.0%chromium, 6.25% to 6.75% nickel, .22% to 30% nitrogen, carbon notexceeding .05%, silicon not exceeding .25%, and remainder essentiallyiron.

8. Hot-rolled alloy steel sheet and strip of good coldforming and goodWelding properties, and of good corrosion-resistance and scalingresistance, and essentially consisting of about: 8% to 16% manganese,19.5% to 23.0% chromium, 5.5% to 9.5% nickel, .20% to .40% nitrogen,carbon not exceeding .05 and remainder essentially iron.

9. Cold-rolled alloy steel sheet and strip having good cold-forming andgood Welding properties, and good corrosion-resistance, and essentiallyconsisting of about: 8.0% to 10.0% manganese, 20.0% to 21.0% chromium,6.25% to 6.75% nickel, .22% to 30% nitrogen, carbon not exceeding .05%,silicon not exceeding .25%, and remainder essentially iron.

10. Alloy steel wire having good cold-forming and good weldingproperties, and good corrosion-resistance and scaling resistance, andessentially consisting of about: 8% to 16% manganese, 19.5% to 23.0%chromium, 5.5 to 9.5 nickel, .20% to .40% nitrogen, carbon not exceeding.05 and remainder essentially iron.

11. Cold-drawn alloy steel wire having good cold-forming and lowrelaxation properties and essentially consisting of about: 8.0% to 10.0%manganese, 19.5% to 21.0% chromium, 6.00% to 7.00% nickel, .22% to 30%nitrogen, carbon not exceeding .05 silicon not exceeding .25%, andremainder essentially iron.

12. In a device for burning the incompletely combusted exhaust gases ofan internal combustion engine, a Welded alloy steel sheet metal housingessentially consisting of about: 8% to 16% manganese, 19.5 to 23.0%chromium, 5.5% to 9.5% nickel, .20% to .40% nitrogen, carbon notexceeding .05%, silicon not exceeding .25 and remainder essentiallyiron.

13. In a mufiler for internal combustion engine exhaust gases, a tightlycoiled alloy steel Wire spring having low relaxation properties andessentially consisting of about:

1 1 8% to 16% manganese, 19.5% to 23.0% chromium, 5.5% to 9.5% nickel,.20% to .40% nitrogen, carbon not exceeding .05%, silicon not exceeding.25 and remainder essentially iron.

References Cited by the Examiner UNITED STATES PATENTS 3,171,738 3/1965Renshaw et al 75--128 References Cited by the Applicant UNITED STATESPATENTS 2,159,725 5/1939 Franks. 2,602,737 7/1952 Binder et a1.2,671,726 3/1954 Jennings. 2,783,169 2/1957 Morgan et al.

12 Cupler. Wasserman et al. Streicher. Kanter et al.

FOREIGN PATENTS Canada.

DAVID L. RECK, Primary Examiner.

1. AN ALLOY STEEL HAVING GOOD HOT-ROLLING, GOOD COLDFORMING, GOODWELDING AND GOOD SCALING RESISTANCE PROPERTIES, SAID STEEL ESSENTIALLYCONSISTING OF ABOUT: 8% TO 16% MANGANESE, 17.0% TO 23.0% CHROMIUM, 5.5%TO 9.5% NICKEL, 20% TO .40% NITROGEN, CARBON NOT EXCEEDING .05%, SILICONUP TO 4.0% OR MORE, AND REMAINDER ESSENTIALLY IRON.